The proposed research is a continuation of ongoing studies of neuronal growth, development, and transmitter phenotypic expression. Using a combination of biochemical, immunocytochemical, pharmacologic, and recombinant DNA techniques, we have defined factors governing embryogenesis in sympathetic and striatal neurons, the fators regulating neurotransmitter phenotypic expression, and the role of intercellular communication in neuronal ontogeny. In particular we have focused on defining the molecular mechanisms regulating cholinergic and peptide neurotransmitter (substance P and somatostatin) development. The present studies will examine mechanisms mediating the effects of cell-cell contact on transmitter expression. They will focus on a membrane protein (MANS) isolated from spinal cord membranes which mediates effects of cell-cell contact on cholinergic and peptidergic development in both sympathetic neurons and spinal cord neurons. Treatment of cultured neurons with MANS stimulates levels of preprotachykinin mRNA and substance P and choline acetyltransferase activity. Specifically we plan to: a) Define the distribution of MANS in the nervous system; b) Characterize the biologic role of MANS; c) Determine whether a membrane receptor mediates the effects of MANS. The proposed studies will also further define the role of cell-cell contact and of soluble differentiating factors in regulating cholinergic spinal neuron development in culture, and will compare mechanisms regulating cholinergic development in different populations of spinal, striatal, and sympathetic neurons. It is hoped that these studies will elucidate mechanisms leading to abnormal development and indicate new therapeutic approaches to diseases of disordered neural development.